This invention relates to the field of medical devices, and more particularly to a guidewire system for advancement through a highly occluded blood vessel.
Atherosclerosis resulting in a blockage of arteries can be a life threatening disease. Percutaneous intravascular procedures such as angioplasty and atherectomy were developed to open blocked vessels with as little trauma as possible. Angioplasty involves inflating a balloon positioned within the obstructive deposits or stenosis in the vessel, so that the stenosis is compressed against the arterial wall and the wall expanded to open up the passageway. Atherectomy involves selective excision and removal of obstructive deposits from the vessel walls.
An essential first step in these percutaneous procedures is maneuvering the distal operative extremity of the angioplasty or atherectomy catheter into position at a precise point inside the arterial occlusion. Maneuvering through small branched vessels and the stenosis itself can be very difficult and tedious. Especially difficult in this respect are chronic total occlusions (CTO). While most CTOs are not totally obstructed, only a small tortuous channel passes through the stenosis.
The guidance system used to position the catheters must be both effective and safe, because if they cannot be positioned precisely into place, the stenosis cannot be treated. Additionally, inadequate guidance carries a risk of perforation of the vessel that exceeds the benefits of recanalization.
The use of a guidewire is ideal in terms of effectiveness, safety, simplicity, and cost. Typically, a guiding catheter is inserted into the patient""s aorta with its distal tip seated in the ostium of the desired coronary artery. The guidewire is then maneuvered into place while its progress is fluoroscopically monitored. Once the guidewire passes through the stenosis, the angioplasty or atherectomy catheters can be advanced over the guidewire and into place within the stenosis.
The distal end of the guidewire-may be shaped, e.g. bent, at an angle up to 90xc2x0 from its longitudinal axis, so that torquing the proximal end of the guidewire from outside the patient can guide the distal tip of the guidewire into branch arteries. While it is known that vibrating a guidewire can help its passage through an occluded artery, such vibration has not been shown to be successful in highly occluded passageways such as CTO""s.
What has been needed is a vibration device with the superior guidewire steerability and ease of use which results from having the guidewire free to rotate or move longitudinally relative to the distal tip of a guiding catheter even though the guidewire is attached to the vibrating mechanism. By providing for simultaneous manipulation of more than one variable of the guidewire, such a device gives the operator greater control over the guidewire position. Furthermore, such a device would have superior ease of use because unclasping, repositioning, and reclasping the guidewire to the vibration mechanism would not be required each time the guidewire needed to be rotated or moved relative to the guiding catheter.
Additional guidewire control would be provided by a guiding catheter with a bend in the distal tip which could be varied incrementally from 0xc2x0 to 90xc2x0 from its axis, while the catheter was inside a patient vessel. When attached to a vibrating device, a catheter with such in situ variability would allow the distal end of the guidewire to oscillate at a variety of angles to the longitudinal axis of the catheter, and would be useful in accessing off-center channels and side branches.
The vibration device of the present invention provides such a combination of desirable properties.
The present invention is directed to a guidewire vibration device for use with or without a guidewire guiding catheter, to aid in advancement of a guidewire through a patient vessel. The vibration device of the invention generally has a guidewire tube reciprocally driven by a motor, designed to provide superior steerability in a reciprocating guidewire.
The vibration device has a housing, an electric motor within the housing, and a cam attached to the motor which translates the motor""s rotational output into repetitive linear motion. A reciprocating member attaches to the cam to vibrate with a pivoting action. A tube is attached to the reciprocating member so that the tube reciprocates with the reciprocating member along the tube""s longitudinal axis but remains free to rotate around the longitudinal axis. A suitable connection is a ball and socket joint formed by a ball on the tube which fits into a socket on the reciprocating member. A guidewire threads through the lumen of the tube, and is releasably attached to the proximal end of the tube.
The rotation of the guidewire tube may be unchecked, or a locking mechanism may be used. A suitable locking mechanism reversibly locks the rotational motion of the tube by adjusting the circumference of an opening through which the guidewire tube extends. When narrowed, the opening is large enough to allow the tube to clear when reciprocating longitudinally but too small to allow corners of the tube to clear if tube rotation is attempted.
In accordance with a further development of the invention a fitting attaches a guiding catheter to the vibration device. The fitting allows the guiding catheter to be reversibly extended or retracted while in use, thereby varying the length that the guidewire extends beyond the distal tip of the catheter without requiring detachment of the guidewire from the vibration device. A suitable fitting has a rotating luer ring threaded onto a distal side of the device, and a tubular support member with a proximal end attached to the rotating luer ring and a distal end attached to a luer fitting which releasably connects a guiding catheter to the tubular member. Rotation of the luer ring imparts longitudinal movement in the catheter but not in the guidewire.
In accordance with a further development of the invention, the vibration device has a variable stroke mechanism that varies the fulcrum of the reciprocating member to vary the reciprocation length. A suitable mechanism has a rotating cap threaded onto the vibration device, and a pivot block attached to the reciprocating member and the underside of the rotating cap. When the cap is rotated, the pivot block is displaced and the fulcrum of the reciprocating member is shifted, thereby varying the angle at which the reciprocating member pivots.
In a preferred embodiment, the vibration device may be used in combination with a guidewire guiding catheter that has support characteristics which can be varied while inside the patient""s vessel. The guiding catheter has an outer tubular member and a inner tubular member slidably disposed within the lumen of the outer tubular member. The distal extremity of the inner tubular member is provided with a curved end which can be reversibly straightened by retracting the inner tubular member distal tip into the distal end of the outer tubular member. The inner tubular member is formed of a plastic material having a modulus of elasticity such that the curve at the distal tip straightens under applied force and subsequently returns when the force is removed. The proximal end of the inner tubular member is attached to the vibration device in a position to receive the guidewire.
The vibration device of the invention provides for ease of use and superior control in advancing a guidewire through a patient vessel. This is due to the ability to rotate the guidewire and vary the length that the guidewire extends beyond the distal tip of the guiding catheter, while the guidewire is still attached to the vibrational mechanism. With prior devices the guidewire could not be manipulated independently of the vibration device, so the operator would have to loosen the clamping mechanism that holds the guidewire to the vibration mechanism, reposition the guidewire, and then reclamp the guidewire to the vibration mechanism. Additionally, the guidewire position inside the vessel could not be manipulated very well with the prior devices because the guidewire would not be vibrated simultaneously with the other manipulations such as rotation. Furthermore, the tediousness of repeatedly releasing, repositioning, and reattaching the guidewire to the vibration mechanism adds to operator fatigue and possibly operator error or engagement with an unsterile area thereby requiring the operator to start over from the beginning with a new sterile guidewire.
The guidewire steering is further optimized by the use of the guiding catheter with a distal tip angle of curvature which can be varied while inside the patient vessel. By enabling the distal end of the guidewire to oscillate at a variety of angles to the longitudinal axis of the catheter, this in situ variability allows off-center channels and side branches to be accessed which otherwise would have been difficult or impossible to enter. These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.